system: Introduce a disjoint UUID type.

Conceptually a UUID is just a bytevector.  However, there's software out
there such as GRUB that relies on the string representation of different
UUID types (e.g., the string representation of DCE UUIDs differs from
that of ISO-9660 UUIDs, even if they are actually bytevectors of the
same length).  This new <uuid> record type allows us to preserve
information about the type of UUID so we can eventually convert it to a
string using the right representation.

* gnu/system/uuid.scm (<uuid>): New record type.
(bytevector->uuid): New procedure.
(uuid): Return calls to 'make-uuid'.
(uuid->string): Rewrite using 'match-lambda*' to accept a single 'uuid?'
argument.
* gnu/bootloader/grub.scm (grub-root-search): Check for 'uuid?' instead
of 'bytevector?'.
* gnu/system.scm (bootable-kernel-arguments): Check whether ROOT-DEVICE
is 'uuid?'.
(read-boot-parameters): Use 'bytevector->uuid' when the
store device is a bytevector.
(read-boot-parameters-file): Check for 'uuid?' instead of 'bytevector?'.
(device->sexp): New procedure.
(operating-system-boot-parameters-file): Use it for 'root-device' and
'store'.
(operating-system-bootcfg): Remove conditional in definition of
'root-device'.
* gnu/system/file-systems.scm (file-system->spec): Check for 'uuid?' on
DEVICE and take its bytevector.
* gnu/system/mapped-devices.scm (open-luks-device): Likewise.
* gnu/system/vm.scm (iso9660-image): Call 'uuid-bytevector' for the
 #:volume-uuid argument.

services: file-system: Use 'file-system->spec'.

* gnu/services/base.scm (file-system-shepherd-service): Use
'file-system->spec' instead of in-line code.

file-systems: Introduce (gnu system uuid).

* gnu/build/file-systems.scm (sub-bytevector)
(latin1->string, %fat32-endianness, fat32-uuid->string)
(%iso9660-uuid-rx, string->iso9660-uuid)
(iso9660-uuid->string, %network-byte-order)
(dce-uuid->string, %uuid-rx, string->dce-uuid)
(string->ext2-uuid, string->ext3-uuid, string->ext4-uuid)
(vhashq, %uuid-parsers, %uuid-printers, string->uuid)
(uuid->string): Move to...
* gnu/system/uuid.scm: ... here.  New file.
* gnu/system/file-systems.scm (uuid): Move to the above file.
* gnu/system/vm.scm: Adjust accordingly.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add uuid.scm.

services: base: Import the closure of (gnu build file-systems).

* gnu/services/base.scm (file-system-shepherd-service): Use
'source-module-closure' in the 'with-imported-modules' form.

file-systems: Add UUID type dictionaries.

* gnu/build/file-systems.scm (uuid->string): Rename to...
(dce-uuid->string): ... this.
(string->uuid): Rename to...
(string->dce-uuid): ... this.
(vhashq): New macro.
(%uuid-parsers, %uuid-printers): New variables.
(uuid->string, string->uuid): New procedures.

vm: Allow partitions to be initialized with a given UUID.

* gnu/build/vm.scm (<partition>)[uuid]: New field.
(create-ext-file-system): Add #:uuid and honor it.
(create-fat-file-system): Add #:uuid.
(format-partition): Add #:uuid and honor it.
(initialize-partition): Honor the 'uuid' field of PARTITION.

gnu: mpg123: Update to 1.25.6 [fixes CVE-2017-12797].

* gnu/packages/mp3.scm (mpg123): Update to 1.25.6.

gnu: libchamplain: Update to 0.12.16.

* gnu/packages/gnome.scm (libchamplain): Update to 0.12.16.

gnu: gnome-online-accounts: Update to 3.24.3.

* gnu/packages/gnome.scm (gnome-online-accounts): Update to 3.24.3.

gnu: emacs: Patch message-mode enriched text translation [security fix].

* gnu/packages/patches/emacs-unsafe-enriched-mode-translations.patch:
New file.
* gnu/packages/emacs.scm (emacs)[source](patches): Add it.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu: nyacc: Update to 0.82.0.

* gnu/packages/mes.scm (nyacc): Update to 0.82.0.

gnu: ruby-activesupport: Update to 5.1.4.

* gnu/packages/ruby.scm (ruby-activesupport): Update to 5.1.4.

gnu: icedtea-8: Install the nss.cfg file to JRE.

Before this, accessing HTTPS will throw an exception about 'nss.cfg' could not
be found.

* gnu/packages/java.scm (icedtea-8)[arguments]: Copy 'nss.cfg' from JDK into
JRE in the install phase.

gnu: gdb: Update to 8.0.1.

* gnu/packages/gdb.scm (gdb): Update to 8.0.1.

download: Adjust main ftp.gnu.org mirror.

* guix/download.scm (%mirrors): Add missing "/gnu" in first mirror,
although that mirror would work even without it.  Use https instead of
http.

gnu-maintenance: Return all the latest tarballs, not just one.

* guix/gnu-maintenance.scm (latest-gnu-release): Return a list of
matching tarballs instead of just the first one.  This gives us .tar.gz,
.tar.xz, etc.

gnu-maintenance: Correctly compare versions.

* guix/gnu-maintenance.scm (latest-gnu-release): Add calls to
'sans-extension'.  This fixes version comparison, which could be fooled
with the ".tar.gz" extension.

gnu: guix: Update snapshot.

* gnu/packages/package-management.scm (guix): Update to a9468b4.

substitute: Download from unauthorized sources that provide the right content.

This allows substitutes to be downloaded from unauthorized servers, as
long as they advertise the same hash and references as one of the
authorized servers.

* guix/scripts/substitute.scm (assert-valid-narinfo): Remove.
(valid-narinfo?): Add #:verbose?.  Handle each case of
'signature-case'.
(equivalent-narinfo?): New procedure.
(lookup-narinfos/diverse): Add 'authorized?' parameter and honor it.
[select-hit]: New procedure.
(lookup-narinfo): Add 'authorized?' parameter and pass it.
(process-query): Adjust callers accordingly.
(process-substitution): Remove call to 'assert-valid-narinfo'.  Check
whether 'lookup-narinfo' returns true and call 'leave' if not.
* tests/substitute.scm (%main-substitute-directory)
(%alternate-substitute-directory): New variables.
(call-with-narinfo): Make 'narinfo-directory' a parameter.  Call
'mkdir-p' to create it.  Change unwind handler to check whether
CACHE-DIRECTORY exists before deleting it.
(with-narinfo*): New macro.
("substitute, no signature")
("substitute, invalid hash")
("substitute, unauthorized key"): Change expected error message to "no
valid substitute".
("substitute, unauthorized narinfo comes first")
("substitute, unsigned narinfo comes first")
("substitute, first narinfo is unsigned and has wrong hash")
("substitute, first narinfo is unsigned and has wrong refs")
("substitute, unsigned narinfo comes first")
("substitute, two invalid narinfos"): New tests.
* doc/guix.texi (Substitutes): Explain the new behavior.

substitute: Make substitute URLs a SRFI-39 parameter.

* guix/scripts/substitute.scm (%cache-urls): Rename to...
(%default-substitute-urls): ... this.
(substitute-urls): New variable.
(guix-substitute): Use it instead of %CACHE-URLS.
* tests/substitute.scm: Likewise.